The present invention relates to a method for optimizing the length of a blank for an open-type clamp and to clamps made with this method, especially clamps provided with an arrangement avoiding any gaps, steps or discontinuities at the internal clamping surfaces.
As explained in my U.S. Pat. No. 6,240,603, the length of the blank for a given nominal size clamp is important for economic reasons. Even if only clamping band material of the order of millimeters can be economized, the overall cost factor becomes significant by reason of the large quantity of mass-produced clamps of this type which amount to hundreds of millions of clamps per year. As also explained in my aforementioned patent, the length of the section of the clamping band from the end of the outer band portion to the beginning of the tightening device, such as a plastically deformable xe2x80x9cOetikerxe2x80x9d ear can be optimized with the use of information well known in the art, depending also on the type of the connection between the inner and outer band portions which are normally provided within this area. This means that any savings in band material must be realized in the selection of the length of the overlapped inner band portion.
As known in the art, arrangements for avoiding gaps, steps or discontinuities at the inner clamping surfaces of open clamps, such as, for example, the step produced at the end of the inner clamping band portion, should be avoided to preclude any likelihood of leakage, especially with the use of relatively hard, thin plastic hoses, as used, for example, in the automotive industry. These arrangements usually involve mutually complementary profiles at the end of the inner band portion and in the overlapping outer band portion interacting in a particular manner. U.S. Pat. No. 4,299,012 to Oetiker discloses one embodiment of such an arrangement which has proved commercially extraordinarily successful in hundreds of millions of clamps and which utilizes a male profile in the form of a tongue-like extension at the inner band end adapted to engage in a female profile formed by an opening in a step-like portion of the outer band portion whereby the height of the step corresponds substantially to the thickness of the clamping band. FIG. 1 of this application illustrates such a clamp of the open type as disclosed in U.S. Pat. No. 4,299,012 in which the clamping band (11) includes overlapping outer and inner clamping band portions (11a and 11b) fixed relative to one another by the mechanical connection consisting of a guide hook (31) and two cold-deformed, deep-drawn support hooks (32) extending outwardly from the inner band portion (11b) and adapted to engage in openings (35) provided in the outer band portion. The tightening device in the form of a so-called xe2x80x9cOetikerxe2x80x9d ear and generally designated by reference numeral (13) includes outwardly extending leg portions interconnected by a bridging portion (16) provided with a reinforcing means (17) of any known type. The outer band portion includes thereby a step-like portion (67) of a height substantially corresponding to the thickness of the clamping band material and provided with an opening for engagement by the tongue-like extension (61) at the end of the inner clamping band portion (11b). The opening is thereby formed by longitudinal cuts (64) extending in the longitudinal direction of the clamping band whereby the material remaining after the cuts can either be pressed-out into a cover (63) or cut off as disclosed in the prior U.S. Pat. No. 4,315,348.
A different approach to the use of a tongue-like extension as shown in FIG. 1 of this application involved a profile with a fork-like configuration at the end of the inner band portion as disclosed in U.S. Pat. No. 4,237,584 to Oetiker. This concept for a stepless arrangement was then adopted in U.S. Pat. No. 4,750,242 to Calmettes et al. in which a profile with a U-shaped configuration at the end of the inner clamping band portion engaged with a so-called boss in the outer clamping band portion and of a shape complementary to the U-shaped configuration. However, the clamp as disclosed in U.S. Pat. No. 4,750,242 involves a potential leakage problem which was resolved with the use of a clamp involving my invention, as disclosed in my copending provisional application Serial No. 60/266,849, filed Feb. 7, 2001, and entitled xe2x80x9cHose Clamp With Internal Clamping Surface Devoid of Steps or Gapsxe2x80x9d and in my copending Utility Application (D/21586) Ser. No. 10/026,715, filed Dec. 27, 2001, and entitled xe2x80x9cMethod of Making Hose Clamps with Internal Clamping Surfaces Devoid of Steps or Gaps and Products Made By Such Method.xe2x80x9d FIG. 2 of this application, in which reference numerals of the 100 series are used, shows a clamp according to my invention as disclosed in the aforementioned copending application which includes a profile with a U-shaped configuration (151, 152) at the end of the inner clamping band portion (111b) adapted to engage with a deep-drawn depression or indentation generally designated by reference numeral (160) with a depth substantially corresponding to the thickness of the band material. The remaining lateral band portions (111xe2x80x2) thereby pass over into the level of the internal clamping surface (160a) at the step-like portions (167) so that the internal clamping surface (160a) and the continuation of the internal clamping surface of the clamping ring (111) continue at the same level. The subject matter of my copending Provisional Application Serial No. 60/266,849 and of my aforementioned Utility Application (D/21586) Ser. No. 10/026,715 are hereby expressly incorporated in their entirety into this application.
It has also been recognized in the prior art that the opening underneath the tightening device, such as a so-called xe2x80x9cOetikerxe2x80x9d ear should be bridged by the full band width of the inner clamping band portion to avoid possible leakage problems as a result of a bulging out of the clamping band under strong internal pressure forces if the gap is bridgedxe2x80x94even only partiallyxe2x80x94by less than the full width inner clamping band portion, for example, by the tongue-like extension as disclosed in German Gebrauchsmuster GM 75 41 277.
The construction of the prior art clamps was based on the belief that any gap underneath the tightening device must be covered by the full width inner clamping band portion at least already at the time the mechanical connection between inner and outer clamping band portions is established and before any tightening of the tightening device has been commenced.
In contradistinction thereto, the present invention is based on the recognition that any gap underneath the tightening device in clamps with a predetermined tolerance range must not be covered in its entirety by the full band width under conditions of established mechanical connection and not-yet-tightened tightening device. Instead, significant savings in clamping band material necessary for a blank can be achieved if the beginning of the complementary profile at the inner clamping band portion away from the free end thereof is located at a predetermined point within the area of the gap with the mechanical connection engaged and with a not-yet-tightened tightening device. This location is determined according to an important feature of this invention by the extent of contraction of the tightening device necessary to produce a predetermined clamping force for the maximum diametric dimension in the tolerance range of a clamp of nominal clamp size.
Accordingly, the method according to the present invention resides in determining the amount of contraction of the tightening device necessary to achieve a predetermined clamping force for the maximum diametric dimension dmax in the tolerance range and to locate the beginning of the complementary profile on the inner clamping band portion in relation to this location as will be described more fully hereinafter.
The clamp produced by the method according to this invention is characterized by the fact that the blank is so configured that the beginning of the complementary profile for the gap-free and stepless arrangement is located in the inner band portion at a particular location within the area of the gap underneath the tightening device which is determined in relation to the extent of tightening of the clamp necessary for realizing a predetermined clamping force for dmax with the mechanical connection engaged and the tightening device tightened to that point.
Accordingly, it is a primary object of the present invention to provide a method and product which permits additional savings in clamping band material for so-called open-type clamps with a tolerance range.